British Ceramic Transactions最新文献

{"title":"Effect of calcium aluminate cement in water on hydration of aluminium powder","authors":"Shaowei Zhang, S. Hashimoto, W. E. Lee","doi":"10.1179/096797804225018723","DOIUrl":"https://doi.org/10.1179/096797804225018723","url":null,"abstract":"Abstract The addition of small amounts (0.25 wt-%) of calcium aluminate cement (CAC) to water greatly accelerates the hydration of Al powder. This behaviour is attributable to the increased basicity of the solution owing to the CAC leading to dissolution of the native Al2O3 film and early hydration products, as well as additional heat released by the accelerated hydration of Al and CAC. The significance of this for the use of Al powder in CAC bonded refractory castables is discussed.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133883583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterisation of borosilicate glass matrix composites reinforced with SiC or ZrO2","authors":"M. Zawrah, A. El-Kheshen","doi":"10.1179/096797804225018642","DOIUrl":"https://doi.org/10.1179/096797804225018642","url":null,"abstract":"Abstract Two kinds of glass/ceramic composites were prepared. The first contained borosilicate glass with SiC ceramic: batches designated SG10, SG20, SG30 and SG40 consisted of 10 : 90, 20 : 80, 30 : 70 and 40 : 60 SiC/glass (wt-%) respectively. The second contained borosilicate glass with ZrO2: batches designated ZG5, ZG10, ZG20 and ZG40 consisted respectively of 5 : 95, 10 : 90, 20 : 80, 40 : 60 ZrO2/glass (wt-%). The densification parameters (bulk density and apparent porosity) were measured by the Archimedes method. Scanning electron microscopy and X-ray diffraction were used to investigate the microstructure and phase composition of the prepared composites. Cold crushing strength was also measured. The results reveal that in composites containing SiC, apparent porosity increases with increasing SiC content, while with increasing firing temperature from 800 to 1000°C, apparent porosity decreases to a minimum at 875°C before increasing again. As SiC content increases, the inhibition of cristobalite formation increases, as shown by XRD. The appearance of cristobalite causes the opposite effect on thermal properties: cold crushing strength increases with increasing SiC content, reaching a maximum at 30 wt-%SiC, and decreases again with 40 wt-%SiC. In ZrO2 containing composites, apparent porosity increases with increasing ZrO2 content. With increasing firing temperature, apparent porosity decreases, reaching a minimum at 1000°C. The effect of ZrO2 on the inhibition of cristobalite formation is more obvious than with SiC. Also, the cold crushing strength of ZrO2 containing composite is higher than for those containing SiC.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115504270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of microstructure on oxygen transport in perovskite type membranes","authors":"S. Diethelm, J. Van herle, J. Sfeir, P. Buffat","doi":"10.1179/096797804225018688","DOIUrl":"https://doi.org/10.1179/096797804225018688","url":null,"abstract":"Abstract The influence of bulk microstructure (grain size distribution, grain boundary length) on the oxygen transport properties of permeation membranes has been investigated. For this purpose, La0.5Sr0.5FeO3-δ samples with different microstructures were prepared by varying sintering time and temperature. Average grain sizes, which ranged from 0.20 to 1.43 μm, were determined by SEM analysis. The oxygen transport properties of the samples were characterised by permeation measurements as a function of temperature in an air/argon oxygen partial pressure gradient. The fluxes presented a change in activation energy, which was attributed to a change in the rate limiting step, from bulk diffusion at lower temperature (< 850°C) to surface limitation at higher temperature (> 900°C). Only transport through the bulk was influenced by the microstructure, with the highest flux for the smallest grains. At 800°C, the fluxes were respectively 0.06, 0.03 and 0.01 μmol cm-2 s-1 through ≈ 1 mm thick samples with average grain sizes of 0.20, 0.63 and 1.43 μm respectively. This would imply that oxygen transport occurs more rapidly along grain boundaries than through the bulk. Grain boundary structure and composition were analysed by TEM.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129103315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Specific heat of Bax Sr1—xTiO3 ferroelectric perovskites","authors":"A. Kumar, U. Naithani, B. Semwal","doi":"10.1179/096797804225018660","DOIUrl":"https://doi.org/10.1179/096797804225018660","url":null,"abstract":"Abstract The specific heat of an anharmonic BaxSr1—xTiO3 ferroelectric crystal is calculated in its paraelectric phase from the Silverman–Joseph Hamiltonian augmented with fourth order phonon coordinates using double time Green's functions. The soft mode contribution to specific heat is described by appropriate Einstein terms. The variation of specific heat with temperature and defect parameters is discussed. The effect of defects on specific heat can be observed in the presence of anharmonicity. Around the Curie temperature the Cochran soft mode is held to be responsible for the anomalous behaviour of specific heat.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123967630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dependence of kaolinite content on particle size distribution in Ugandan kaolin clay","authors":"Y. Kaahwa, F. D’ujanga","doi":"10.1179/096797804225012882","DOIUrl":"https://doi.org/10.1179/096797804225012882","url":null,"abstract":"Abstract Semiprocessed kaolin clay was sieved through sieves of various particle size ranges. Particle size distribution was determined using a Malvern laser particle sizer and kaolinite content in each particle size range was determined by X-ray diffractometry. It was found that kaolinite content increased with decreasing particle size range.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114517618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Towards biologically inspired materials","authors":"G. Babini, A. Tampieri","doi":"10.1179/096797804225012828","DOIUrl":"https://doi.org/10.1179/096797804225012828","url":null,"abstract":"Abstract The development of a synthetic bone substitute able to mimic both the chemical composition and morphology of bone's inorganic component is a priority for biomaterials research. Hydroxyapatite is a promising material for this application. The role of nanostructured apatites in the design and preparation of biomimetic and bioactive scaffolds is particularly crucial. These new materials chacterised by nanodomain and modified chemical features show improved performance in terms of interaction with natural tissue, allowing and taking part in bone ingrowth. Thus interest has shifted from biocompatible to biomimetic and bioactive materials. The importance of non-stoichiometric/defective apatites similar to the mineral part of bone, in particular those containing HPO42- CO32- and Mg2+, is explained. Attention is focused on innovative synthesis techniques that can yield powders with higher reactivity to build synthetic implants with a porous structure resembling that of spongy bone that can ensure complete penetration and consequent replacement of the bony tissue. The use of cellulosic sponges soaked with powder suspensions can give adequate porosity in terms of both size and distribution, and this appears to be a suitable method for the repair of both loadbearing and nonloadbearing osseous defects. Such sponges can also function as in situ drug delivery systems if they are charged with pharmacologically active compounds. So far the characteristics of artificial bone tissues have been shown to be very different from those of natural bone, mainly because of the absence of the self-organising interaction between apatites and the proteinic component that modifies the intrinsic features of each constituent. For that reason attention is currently focused on so called biologically inspired materials, in this case composites synthesised to exploit the ability of biological systems to store and process information at the molecular level. Following this new approach, nanosize bladelike crystals of hydroxyapatite have been nucleated in situ on self-assembling collagen fibres. The characteristics of the resulting composites are described.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114178419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of microstructural evolution during nitridation of aluminium using simultaneous thermal analysis","authors":"E. Salahi, J. Heinrich","doi":"10.1179/096797804225012909","DOIUrl":"https://doi.org/10.1179/096797804225012909","url":null,"abstract":"Abstract Aluminium powders with different average particle sizes were synthesised into aluminium nitride in nitrogen atmosphere using simultaneous thermal analysis (TG/DTA). Experiments showed that reaction of Al powders started below the melting point of aluminium (660°C) in the solid–gas state, however most of the reaction took place above the melting point, in the liquid–gas state. Further conversion of Al to AlN took place up to 1200°C. The influence of particle size on the nitridation process was demonstrated by the use of different Al powders. Microstructural characterisation showed that two kinds of whisker were formed in the original Al powder bed, one with wool-like morphology and the other with needlelike morphology and sharp changes of direction.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114273399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of calcium aluminate cement in magnesia castable on total oxygen content of interstitial free steel","authors":"N. Li, Huili Li, Y. Wei","doi":"10.1179/096797804225018750","DOIUrl":"https://doi.org/10.1179/096797804225018750","url":null,"abstract":"Abstract Samples of interstitial free (IF) steel buried in MgO castable bonded by calcium aluminate cement (CA) in graphite crucibles were heated at 1600°C for 90 min. Total oxygen content (TOC) of the steel was examined after heating and the refractory was investigated by SEM and EDS. It was found that TOC was higher in IF steel samples in contact with MgO castables containing 3 or 5 wt-% CA than with castables containing 7 wt-% CA or without CA. A liquid layer formed between refractory oxide and molten steel separates the refractory oxides from molten steel and inhibits direct dissolution of oxides in the molten steel. Transfer of oxygen between the refractory oxide and molten steel occurs by the formation of CaO.Fe2O3 at the boundary between the refractory oxide and the liquid layer, diffusion of CaO.Fe2O3 in the liquid phase layer, decomposition of CaO.Fe2O3 and dissolution of FeO into the molten steel. W ith increasing CA content in MgO based castables the CaO content in molten steel increases, but iron oxide content decreases, leading to the result mentioned above.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133214837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machining high quality superconducting rings from top seeded melt grown samples","authors":"H. González-Jorge, J. Peleteiro, G. Domarco","doi":"10.1179/096797804225012846","DOIUrl":"https://doi.org/10.1179/096797804225012846","url":null,"abstract":"Abstract A drilling procedure for obtaining superconducting rings from top seeded melt grown samples is reported. The method described is based on the use of a column drilling machine with a copper–diamond drill bit. Modifications have been made in order to avoid structural damage to the superconductor during drilling. The success of the technique was assessed by measuring the critical current of samples before and after machining, with similar values obtained in both cases.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128130596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Damage of monolithic refractory linings in steel ladles during drying","authors":"N. Schmitt, Y. Berthaud, J. F. Hernandez, P. Meunier, J. Poirier","doi":"10.1179/096797804225012873","DOIUrl":"https://doi.org/10.1179/096797804225012873","url":null,"abstract":"Abstract Safety linings of steel ladles are made of high content alumina castable. In situ observations confirm that during drying a network of macrocracks appears in the monolithic castable lining, owing to both dehydration of the cement paste and temperature. Crack formation kinetics have been characterised over the life of the lining. To simulate the behaviour of the lining, the thermomechanical behaviour of the castable was characterised in compression and three point bend tests, thermal dilatation tests and TGA analysis in the 20–600°C temperature range. The change in properties is shown to be due mainly to transformation of hydrates in the castable. Numerical simulations of the lining drying process were also performed using a finite element code to verify the causes of cracking. A parametric study was carried out to examine the possibility of reducing the stresses induced by thermal loading. Improved thermal insulation and better control of heating reduce the risk of failure in the lining.","PeriodicalId":350675,"journal":{"name":"British Ceramic Transactions","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124113198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}